1. Field of the Invention
This invention relates to optical microscope imaging and measurement systems and more particularly to a system and a method of processing optically measured data.
2. Description of Related Art
D. Nyyssonen, J. Seligson and I. Mazor, "Phase Image Metrology with a Modified Coherence Probe Microscope," Proc. SPIE Vol. 1926-23, pp 299-310 (1993) describes a coherence probe microscope measurement prior art system.
V. Tychinsky and A. Tavrov describe in "Optical 3D Monitoring VLSI Structures" PROC. SPIE Vol. 1673, pp. 483-485 (1992) the use of phase images for CD (critical dimension) measurement. The phase images were obtained with a HeNe laser (632.8 nm) and a Linnik interferometer. Their results show an increase in resolution based on scalar theory simulations and experimental data.
E. C. Kintner, "Method for the Calculation of Partially Coherent Imagery," App. Opt. 17, pp. 2747-2753 (1978), which pertains to scalar image modeling describes a method using Fourier transforms to model the performance of a 1-D optical system with aberrations or apodization.
D. Nyyssonen and C. Kirk, "Optical Microscope Imaging of Lines Patterned in Thick Layers with Variable Edge Geometry: Theory," J. Opt. Soc. Am. A 5, pp. 1270-1280 (1988) describes a monochromatic waveguide model that can predict the optical microscope images of line objects with arbitrary edge geometry. The article pertains to vector image modeling which is pertinent because scalar image calculations cannot accurately predict images of thick objects where mode coupling occurs. Both of these references use Fourier transform techniques to compute images.
M. Davidson, K. Kaufman and I. Mazor, "First Results of a Product Utilizing Coherence Probe Imaging for Wafer Inspection," Proc. SPIE Vol. 921, (1988) describes a white light coherence probe microscope measurement system.
D. Nyyssonen, "Narrow-Angle Laser Scanning Microscope Systems for Linewidth Measurements on Wafers," NISTIR 88-3808, pp 1-107 (Jun. 1988) states at page 12, states that a thickness of 180-nm SiO.sub.2 on a silicon wafer produces a nearly pure phase image which has been shown to be sensitive to small amounts of optical aberrations.